linux-kernel - Re: [PATCH RFC] rxe: Fix iova-to-va conversion for MR page sizes != PAGE

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Message-ID: <20260106010159.GN125261@ziepe.ca>
Date: Mon, 5 Jan 2026 21:01:59 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Li Zhijian <lizhijian@...itsu.com>
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	zyjzyj2000@...il.com, leon@...nel.org,
	Yi Zhang <yi.zhang@...hat.com>
Subject: Re: [PATCH RFC] rxe: Fix iova-to-va conversion for MR page sizes !=
 PAGE_SIZE

On Fri, Dec 26, 2025 at 05:52:37PM +0800, Li Zhijian wrote:
> The current implementation incorrectly handles memory regions (MRs) with
> page sizes different from the system PAGE_SIZE. The core issue is that
> rxe_set_page() is called with mr->page_size step increments, but the
> page_list stores individual struct page pointers, each representing
> PAGE_SIZE of memory.
> 
> Problem scenarios with concrete examples:
> 
> 1. mr->page_size > PAGE_SIZE (e.g., 64K MR with 4K system pages):

Why does RXE even have mr->page_size at all?

Real HW has this value to optimize for large page sizes, but I'm not
sure we really need this for RXE..

Jason